// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_FILE_DESCRIPTOR_POSIX_H_
#define BASE_FILE_DESCRIPTOR_POSIX_H_

#include "base/files/file.h"
#include "base/files/scoped_file.h"

namespace base {

// -----------------------------------------------------------------------------
// We introduct a special structure for file descriptors in order that we are
// able to use template specialisation to special-case their handling.
//
// IMPORTANT: This is primarily intended for use when sending file descriptors
// over IPC. Even if |auto_close| is true, base::FileDescriptor does NOT close()
// |fd| when going out of scope. Instead, a consumer of a base::FileDescriptor
// must invoke close() on |fd| if |auto_close| is true.
//
// In the case of IPC, the the IPC subsystem knows to close() |fd| after sending
// a message that contains a base::FileDescriptor if auto_close == true. On the
// other end, the receiver must make sure to close() |fd| after it has finished
// processing the IPC message. See the IPC::ParamTraits<> specialization in
// ipc/ipc_message_utils.h for all the details.
// -----------------------------------------------------------------------------
struct FileDescriptor {
    FileDescriptor()
        : fd(-1)
        , auto_close(false)
    {
    }

    FileDescriptor(int ifd, bool iauto_close)
        : fd(ifd)
        , auto_close(iauto_close)
    {
    }

    FileDescriptor(File file)
        : fd(file.TakePlatformFile())
        , auto_close(true)
    {
    }
    explicit FileDescriptor(ScopedFD fd)
        : fd(fd.release())
        , auto_close(true)
    {
    }

    bool operator==(const FileDescriptor& other) const
    {
        return (fd == other.fd && auto_close == other.auto_close);
    }

    bool operator!=(const FileDescriptor& other) const
    {
        return !operator==(other);
    }

    // A comparison operator so that we can use these as keys in a std::map.
    bool operator<(const FileDescriptor& other) const
    {
        return other.fd < fd;
    }

    int fd;
    // If true, this file descriptor should be closed after it has been used. For
    // example an IPC system might interpret this flag as indicating that the
    // file descriptor it has been given should be closed after use.
    bool auto_close;
};

} // namespace base

#endif // BASE_FILE_DESCRIPTOR_POSIX_H_
